1. Field of the Invention
This invention relates generally to dispensing tools for dispensing multiple component adhesive mixtures such as those used to bond a metal anchor within solid masonry. More particularly, it relates to a dispensing device which includes improved pistons constructed to uniquely interact with an end cap of a cartridge chamber of the dispenser so as to effectively maintain a sealing relationship with the chamber as the mixture is dispensed.
2. Description of the Prior Art
For the dispensing of viscous fluids, such as two-part epoxy components and the like, the prior art includes dispensing devices which consist of a frame for holding a cartridge assembly having two separate cylindrically-shaped chambers, a dispensing nozzle attached to one end of the cartridge assembly, and a combination cartridge end seal and plunger movably disposed within each of the two chambers. A pair of pistons and corresponding parallel piston rods are carried by means of the frame. A third push rod, disposed parallel to the piston rods, is attached to the piston rods at one end by means of a connecting plate. Axial forces applied to the push rod are transferred to the piston rods through means of the connecting plate. As the respective piston rods and pistons are moved forward into the corresponding cartridge chambers and towards the nozzle, the pistons make contact with the cartridge plungers which, in turn, force the viscous fluids of the cartridge assembly out of the nozzle.
As is generally well known, considerable force is required, dependent upon the viscosity of the fluids being dispensed, for ejecting the fluids out of the cartridge assembly. Accordingly, high pressure is exerted by means of the fluids upon the respective pistons and also upon the cartridge chamber walls. Due to this pressure acting upon the cartridge chamber walls, the chambers tend to expand radially so that a certain amount of radial play develops between the pistons and the corresponding chambers. Such radial play tends to cause a loss of sufficient sealing and thus a portion of the fluids being dispensed can escape out of the rear end of the chambers. Prior to the present invention, no satisfactory piston for use with a cartridge plunger disposed within a cartridge has been available which operates to provide sufficient sealing under high pressure conditions.
A state of the art search directed toward the subject matter of this application was conducted in the U.S. Patent and Trademark Office and revealed the following patents: U.S. Pat. Nos. 3,029,985; 3,250,443; 3,493,147; 4,432,473; 4,645,093; and 4,678,107. However, none of the prior art uncovered in the search disclosed a dispensing device for multiple adhesive mixtures having plunger assemblies like that of the present invention which produces a sufficient sealing effect under high pressure dispensing conditions.